linux-kernel - Re: Regarding 711f8c3fb3db "Bluetooth: L2CAP: Fix accepting connection request for invalid SPSM"

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Message-ID: <Y48sR0xv0yuH8GDd@kroah.com>
Date:   Tue, 6 Dec 2022 12:49:27 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Cengiz Can <cengiz.can@...onical.com>
Cc:     Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: Regarding 711f8c3fb3db "Bluetooth: L2CAP: Fix accepting
 connection request for invalid SPSM"

On Tue, Dec 06, 2022 at 02:27:27PM +0300, Cengiz Can wrote:
> Hello Luiz Augusto,
> 
> 
> I'm by no means a bluetooth expert so please bear with me if my
> questions sound dumb or pointless.
> 
> 
> I'm trying to backport commit 711f8c3fb3db ("Bluetooth: L2CAP: Fix
> accepting connection request for invalid SPSM") to v4.15.y and older
> stable kernels. (CVE-2022-42896)
> 
> 
> According to the changes to `net/bluetooth/l2cap_core.c` there are two
> functions that need patching:
> 
> 
> * l2cap_le_connect_req
> * l2cap_ecred_conn_req
> 
> 
> 
> Only the former exists in kernels <= v4.15.y. So I decided to skip
> 
> l2cap_ecred_conn_req for older kernels.
> 
> 
> Do you think this would be enough to mitigate the issue?
> 
> 
> 
> If so, older kernels also lack definitions of L2CAP_CR_LE_BAD_PSM and
> 
> L2CAP_PSM_LE_DYN_END.
> 
> 
> I see that L2CAP_CR_LE_BAD_PSM is basically the same as
> L2CAP_CR_BAD_PSM so I used it to signify an error.
> 
> 
> I think it should be enough for the sake of a backport.
> 
> 
> What do you think?

I've already done this backport and it is in the latest -rc1 stable
kernel releases.  Is it not working for you there?  Why do it again?

thanks,

greg k-h